/Engine/Source/Runtime/Core/Public/Misc/CoreDelegates.h
Some platform have a System UI Overlay that can draw on top of the application. The game might want to be notified so it can pause, etc... Parameter (bool) should be true if the system UI is displayed, otherwise false should be passed
static [TMulticastDelegate](API\Runtime\Core\Delegates\TMulticastDelegate)< void(bool)> ApplicationSystemUIOverlayStateChangedDelegate;